This proposal seeks to understand the way in which honeybees process components of an odorant blend. Behavioral studies of attention have made good use of a learning paradigm called "blocking" to study attention in non-human animals. As a model, the honeybee represents an invertebrate system that has been well studied. Several lines of experimental evidence indicate that blocking in bees occurs centrally rather than in the peripheral sensory cells of the antenna. As the first sensory processing center after the antenna, the antennal lobes may be the site at which synaptic plasticity leads to blocking. This work will focus on the antennal lobes. Recently, a model of the antennal lobe by Linster and Smith has been used to investigate the role of the antennal lobe central circuitry in extracting essential elements from odorant blends, initial behavioral experiments will establish standardized sensory input, the degree of generalization between odorants based on the two parameters chain-length and functional group and the degree of blocking between similar odorants. The behavioral experiments will lay the ground work for the subsequent physiological experiments. Changes in signalling in the antennal lobes before and after blocking will be measure using intracellular recording techniques from the interneurons and projections. The similarity in neural architecture between the insect antennal lobe and the vertebrate olfactory bulb may make the bee an excellent model for elucidating the phenomenon of attention.